Grease compositions containing an antirust



United States Patent GREASE COMPOSITIONS CONTAINING AN ANTIRUST RobertL. 'Merker, Washington, D. C.

No Drawing. Application March 27, 1951, Serial No. 217,900

9 Claims. Cl. 252-40 (Granted under Title 35, U. s. Code 1952 sec. 266

This invention relates to improved greases embodying an antirusting:agent .as part of the composition. The greases to which the inventionrelates are those in which a metal soap is used in thickening thelubricating fluid. The invention also relates to metal soaps containingan antirust ing agent.

Rusting of steel parts is often encountered where greases are used asthe lubricant. Moisture deposited on the grease is transferred to thelubricated steel surface by the conjoint action of the soap and themoving part. The soap acts in the role of emulsifier for the water whichis brought into emulsion with the lubricating fluid and subsequentlymoved to the steel surface through the continual Working of the .greaseby the moving part. Corrosion by rusting also may occur in the case ofironbearin'g parts packed with grease for storage or shipment where thegrease film, either initially or through accidental rubbing ofl, isquite thin. In such case, moisture, such as rain, or condensate from theatmosphere, can penetrate through the thin grease film to cause rustingof the iron bearing surface.

I have found that protection against rusting can be incorporated ingreases when there is added to the grease a water-soluble salt ofcertain carboxylic acids hereinafter more fully identified.

According to the present invention, greases having antirust propertiescan be obtained by providing in the grease a water-soluble salt of analkyl monocarboxylic acid of 6 to carbon atoms or of an alkylenedicarboxylic acid of 7 to carbon atoms. The hydrocarbon group of theacids may be branched or unbranched. The water-soluble salt is theneutral salt of the dicarboxylic acids. Suitable carboxylic acids forforming the acid portion of the salts are, for example, hexanoic,heptanoic, octanoic, 2- nonanoic and decanoic acid of the monocarboxylicseries and pimelic, suberic, tetramethyl succinic, azelaic, heptylmalonic, butyl adipic, sebacic, dodecanedioic, tetradecanedioic andhexadecanedioic acid of the dicarboxylic series. A preferred group ofacids for the salts are the dicarboxylic acids having from 8 to 10carbon atoms, e. g., suberic, azelaic and sebacic acids. Thesalt-forming group of the water-soluble salts may be taken, for example,from the alkali metals, the alkaline earth metals, ammonium, andwater-soluble amines. The sodium salts constitute a preferred group ofthe water-soluble salts of the afore-defined classes of carboxylic acidsfor preparing the improved greases of the invention.

These antirust salts are not soluble in the greases or the soap used forthickening the same, and accordingly, are dispersed therein by somesuitable means, as, for example, by milling the grease with the salt infinely divided form on a three roll 1nill.. The amount of the salt addedmay be varied somewhat depending upon the degree of rust preventiondesired and the activity of the particular salt selected. In general itwill be found that between about .05% and about 0.2% by weight of thesalt on the grease will be found sufficient to give complete protectionagainst rusting of iron-bearing surfaces lubricated 2,722,516 PatentedNov. 1, 1955 with the greases. Instead of adding the salt to the grease,it may be incorporated in the soap which is then used for thickening ofthe lubricating fluid to form the grease.

The water-soluble salts function in the grease as antirusts bydissolving in the water at the metal surface to form a salt solutionfrom which the salt is preferentially adsorbed to the metal surface toform a layer thereon constituting a barrier between the metal and thewater.

The invention is further illustrated by the results appearing in thetable below and obtained from comparative corrosion tests in which aseries of water-soluble salts were employed including certain of theabove defined carboxylic acid salts. The tests were performed byimmersion of a clean, cold rolled steel strip (1%" X A) in a water (tap)solution of the salt for the stated periods of time at a temperature ofC. The pH of all the salt solutions was approximately 8.

Table I Appearance of Metal Specimen After- Percent Salt Wfeisgliit o a1,000 31mins 24h0urs hours hours ZSod. shenzoate 0. 2 :Socl. ,phenolate"0. 2 I Sod. acetate 0. 2, o. Sod. ilaurate. 0. 2 L slight rust, muchrust Sod..stearate 0.2 very slight; slight rust" rus :Sod.l1exanoate0.2. norust no rust... no rust. no rust. Sod.heptanoate 0.2 do Do. Sod.'2-nonano- 0.2 do.... Do.

ate. Sod. oxalate... 0. 2 Sod. malonatc... 0. 2 Sod. succinate 0.2 Sod.adipate 0. 2 Sod. suberate. 0. 2 no rust.

0.2 Do. 0.2 do. do Do. 0.2 slight rust much rust.

N. B. Test discontinued in runs where positive evidence of rusting. Th;sodium salt of the indicated dicarboxylic acid 15 the neutral salt ineac case.

Under the same conditions and using as inhibitor, respectively,potassium, lithium, calcium, barium, strontium, magnesium, methyl andisopropyl amine azelates (neutral salts) in a concentration of slightlyless than 0.2% by weight, no rusting of the steel strip was observedeven after a period of 100 hours immersion in the aqueous solution ofthe salt.

The rust inhibitors of the present invention can be used in a widevariety of greases both from the standpoint of the lubricating fluid andthe soap used as thickener. The most common greases are those in which apetroleum oil is thickened with sodium or calcium stearate. However, theinhibitors may not only be used effectively in these common greases butlikewise in greases in which the lubricating fluid is of syntheticorigin, such as the diesters (alkyl esters of alkylene dicarboxylicacids), silicones, and polyalkylene oxide fluids, e. g.,polyisopropylene oxide, which have been stoppered at both ends with analkyl group, e. g., butyl, and the thickener is a metal soap of other,limitedly water-soluble higher fatty acids, e. g., lithium palmitate,aluminum stearate, etc.

Since various changes may be made in the practice of the inventiondescribed herein Without departing from the spirit or scope thereof, itis to be understood that the foregoing description is intended by way ofillustration and not in limitation of the invention.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. An improved lubricant grease comprising a base lubricating fluidthickened with a metal soap and containing a small, rust-inhibitingproportion of a watersoluble neutral salt of an alkylene dicarboxylicacid of 8 to carbon atoms in which the carboxylic acid groups are linkedto the opposite terminals of an alkylene chain of from 6 to 8 carbonatoms.

2. An improved lubricant grease comprising a base lubricating fluidthickened with a metal soap and containing a small, rust-inhibitingproportion of a neutral alkali metal salt of an alkylene dicarboxylicacid of 8 to 10' carbon atoms in which the carboxylic acid groups arelinked to the opposite terminals of an alkylene chain of from 6 to 8carbon atoms.

3. An improved lubricant grease comprising a base lubricating fluidthickened with a metal soap and containing a small, rust-inhibitingproportion of the neutral sodium salt of an alkylene dicarboxylic acidof 8 to 10 carbon atoms in which the carboxylic acid groups are linkedto the opposite terminals of an alkylene chain of from 6 to 8 carbonatoms.

4. An improved lubricant grease comprising petroleum lubricating oilthickened with an alkali metal soap and containing a small,rust-inhibiting proportion of the neutral sodium salt of an alkylenedicarboxylic acid of 8 to 10 carbon atoms in which the carboxylic acidgroups are linked to the opposite terminals of an alkylene chain of from6 to 8 carbon atoms.

5. An improved lubricant grease comprising petroleum lubricating oilthickened with an alkaline earth metal soap and containing a small,rust-inhibiting proportion of the neutral sodium salt of an alkylenedicarboxylic acid of 8 to 10 carbon atoms in which the carboxylic acidgroups are linked to the opposite terminals of an alkylene chain of from6 to 8 carbon atoms.

6. An improved lubricant grease comprising a petroleum lubricating oilthickened with an alkali metal soap and containing a small,rust-inhibiting proportion of sodium suberate.

7. An improved lubricant grease comprising a petroleum lubricating oilthickened with an alkali metal soap and containing a small,rust-inhibiting proportion of sodium azelate.

8. An improved lubricant grease comprising a petroleum lubricating oilthickened with an alkali metal soap and containing a small,rust-inhibiting proportion of sodium sebacate.

9. An improved lubricant grease comprising petroleum lubricating oilthickened with a metal soap and containing a small, rust-inhibitingproportion of a water-soluble neutral salt of an alkylene dicarboxylicacid of 8 to 10 carbon atoms in which the carboxylic acid groups arelinked to the opposite terminals of an alkylene chain of from 6 to 8carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS2,363,514 Farrington et a1 Nov. 28, 1944 2,363,515 Farrington et al Nov.28, 1944 2,363,516 Farrington et al Nov. 28, 1944 2,368,602 Weiss Jan.30, 1945 2,426,496 Farley Aug. 26, 1947 2,457,586 McGrogan Dec. 28, 19482,481,372 Fuchs Sept. 6, 1949 2,487,080 Swenson Nov. 8, 1949 2,495,651Butcosk Jan. .24, 1950 2,528,373 Knowles et al. Oct. 31, 1950 2,539,503Zisman et al. Jan. 30, 1951 2,583,607 Sirianni Jan. 29, 1952

1. AN IMPROVED LUBRICANT GRASE COMPRISING A BASE LUBRICATING FLUIDTHICKENED WITH A METAL SOAP AND CONTAINING A SMALL, RUST-INHIBITINGPROPORTION OF A WATERSOLUBLE NEUTURAL SALT OF AN ALKYLENE DICARBOXYLICACID OF 8 TO 10 CARBON ATOMS IN WHICH THE CARBOXYLIC ACID GROUPS ARELINKED TO THE OPPOSITE TERMINALS OF AN ALKYLENE CHAIN OF FROM 6 TO 8CARBON ATOMS.